Improvement in bridges



` thereof.

i? textit/d niet '1t/atleti., @it

`JAMIEs 13..HEA.Ds,or sT. Louis, MISSOURI.

" Leners Patent N0.s9,745, zaad MWA, 1869, s'

IMPROVEMENT IN BRIDGES.

The Schedule referred to in these Letters Patent'and making part of the saure.y

To lall whom it mar/y concern.- f

Be it known that I, JAMES B. Enns, ofthe city of St.. Louis,in the county of St. Louis, and `State of `Missouri, have made certain new and useful Improvem'ents in Securing the Piers o1' Intermediate Supports of Arched Bridgesagainst Oscillatious; and I do hereby declare that thefollowingis afull and clear description thereof, reference being had to the accompanying drawings, and to the letters of reference marked thereon. I

It is Well known that in arched bridges, having more than one span, andtherefore needing piersor intermediate supports, such piers are subject to great I'i',hrusts,lt ;ending tomovethe same inthe direction of the `longitudinal bridge-axis, wheneverthe transient load upon `the bridge is not equallydistributedon the several spans. `And, said ythrusts become a maximum 4when one or more spans are under action of th'e maximum load, which can be placed thereomand the adjacent span is subject only to the action of its own Weight.

In this case, the arch or arches under greatest strain flatten, and thereby'increase in span', thusforcing the i adjoining pier orv piers toward thesucceeding arches,V

compressing the same, until the thrustv is finally ref lceived lby the abutment.

t is also known` thatthe oscillationsof piers thus construction Vnecessitates great cost, and causes great diiiiculties 1n` securing foundations, owing totheir great n area,rand the superincumbent Weight.k Y

`In view hereof, the'nature offthis invention is inl connecting-the upper ends of vthe pierswith the fixed abutments, by means of thrustbars,receiving on said `bars the strains caused by unequallydistributed weights and affectingthe'piers to. cause oscillations. p

And the 'nature of said invention, therefore, requires n l the constructionof said piers as beams held at the pierfoundation, and at upper ends .by the tlirust-bars, and subject, at the 'spring-line ofthe arches, to the thrust of saidarches..

The nature of-thisinvention is furthcrin 'such con# struct-ion of the thrust-bars, and their connection-withtle piers and abutments, as shall enable `thesarne to act properly underall contingencies of temperature.

c It is believed that in the successful development and construction of the vfeatures of my said invention,

thesaid piers may be reduced to an absolute minimum 'of size and cost consistent with safety.

i To enable `those skilled herein Vto `make and us'emy' said improvement, I will now give a detail description thereof, referring tol Figure las au elevation, and to L y Figure 2.asa plan, showing vthe generalfeatures Afrepresents the abutments, constructed in thel usual substantial manner, to`resist` the thrust of the metallic or wooden-arches B B.

G represents the intermediate support or pier.

Thearches B B carry the loads which are placed thereon in the manner usual, aud-this invention in nowise relates to any special construction of said arches, or of the roadway resting on said arches.

It is. plain that if the transient load should cover the roadway on the arch B, the samewo'ulddeect and thrust the pier O toward the arch B, unless said pier were of such great Weight as, to resist said thrust.

In order that said pier may be built of a very light and economical form, I prevent the. movement of the same by .the thrustabars D D', which transmit the thrust to the `abutmentsA.

And in order that the expansion or contraction of k the bars D D', when the same are metallic, shall not interrupt their eective action, I arrange the bars D` and D to connect by the pins d andd with the compensation-lever E, this being secured bythe journalpinV e to the pier G.

` The bars D D' may be secured to the abutmentsY in lany strong and 'durable manner. v g I l Whenever the bars D and D are of equal length, the arms'l of the lever E, at Whichthey-act, will be equal but as any inequality in the length of said bars D D' causesthern to expand and'contract unequally, the arms of the lever E must then be proportionate to the expansion of said bars; thus the journal cwill.

hold the pier C as a fixed point.

Now,'as the pier G is held at its upper end `bythe I ,thrust-bars D D', and 4at its lower end by its foundation-support, andis subject to the thrust of the arches B B', it is plain that the said pier must be constructed as a beam, capable of resisting the strain received as aforesaid.

In case that there are several intermediate piers,`

the thrust-bars D D will, in each instance, reach to the abutments, and this condition of the problem in'- volves, therefore, merely a multiplication of the devices D `D' and E. l,

Owing tothe height of the points of connection of lthe bars I) D', abovethe' archesV B B', the strains in the said bars will be much less than the thrusts of said arches. Again, as the 4roadway may be arranged to act with thrust-bars, thedetails of execution may be achieved with great economyr- Having thus fully described my invention, What I claim, is

f 1. The thrust-bars D D' and compensatinglever E, A

when applied to prevent oscillations of the pier- G, substantially as set forth. g

2. Giving to bridge-piers, which are supported and held at their foundations, and which resist the thrusts of arches, an additional support by rods connecting f their upper ends with ,each other and with the abut-` ments, substantiallyas set forth.

Witnesses:

M. RANDOLPH, GEO. P..HERTHEL, Jr.

JAS. n.A Enns.` 

